Mobile communication devices are nearly ubiquitous today. As the devices are mobile, in addition to providing communication capabilities, a mobile device may also provide information regarding a location of the mobile device, e.g., to assist various applications to provide a variety of services to a user of the mobile device. The mobile device, such as a user equipment (UE), may be configured to perform positioning techniques to determine the location of the UE and/or to provide information to another device, e.g., a location server, that determines the location of the UE. For example, the UE or location server may use multilateration techniques to determine the location of the UE. To perform or assist with multilateration, the UE receives and analyzes positioning signals from multiple signal emitters, e.g., base stations, located at known locations. One example of a positioning technique that uses multilateration is Observed Time Difference Of Arrival (OTDOA), that uses differences in arrival times of positioning signals (e.g., positioning reference signal (PRS)) received by the UE from the multiple base stations to determine the location of the UE. A PRS may be referred to herein as a PRS signal and multiple PRSs may be referred to herein as PRS signals.
In order to perform OTDOA, or other positioning techniques, the location of the emitters and other information about the PRS signals are used. This information is provided to the UE in the form of assistance data. Assistance data may be sent from a serving base station to the UE from a location server associated with the network, or the assistance data may be received from a third party server. The assistance data may help the UE acquire the positioning signals, e.g., by providing search windows of time when the PRS signals should arrive at the UE.
Techniques other than multilateration with OTDOA may be used to determine a location of a mobile device. For example, trilateration using distances to several known locations, e.g., of base stations, may be used with ranges to the base stations determined by measuring signal strengths of received signals and determining their transmission strengths.